In control terminology, what is the main purpose of a controller?

The main purpose of a controller in control systems is to maintain the desired state of the system. This involves continually monitoring the process variable (the actual state of the system) and comparing it to the desired setpoint (the target state). The controller then calculates the error, which is the difference between the setpoint and the process variable, and produces an output to correct any deviations from the desired state. This regulation ensures that the system operates within specified limits and performs optimally.

While physically manipulating the system, interpreting sensor data, and serving as a backup system are important functions in the context of control systems, they are not the primary role of the controller itself. The controller's primary function remains centered on maintaining stability and achieving target performance levels throughout system operations.